FWIW, to avoid using the --prefix option, you can set your PATH / LD_LIBRARY_PATH to point to the Open MPI installation on all nodes.

Many organizations opt to have NFS-shared home directories, so that when you modify your "main" shell startup file (e.g., .bashrc) to point PATH and LD_LIBRARY_PATH to your Open MPI installation, it effectively modifies it for all nodes in the cluster.